10k DLC means 10 karat diamond-like carbon.
10 karat is the lowest karat gold (41.6%) that can still be sold as “gold” in the US. DLC (diamond-like carbon) can be applied as a coating on almost any material that is compatible with the vacuum in which it is typically produced.
When used in pure form, DLC is as hard as natural diamond or can be even harder. In pure form these DLC coatings offer protection against abrasive wear and attack from atmospheric moisture and chemical vapors.
See a huge collection of jewelry maker's marks and hallmarks at university.langantiques.com.
Most of the time, gold can be marked in several ways. Gold jewelry is often pounded with specific marks that offer information on its fineness.
These marks assist the consumer to find out the value and genuineness of every piece of jewelry. Most jewelry has at least one mark specifying the content of the gold.
Here's how to understand the meaning of gold hallmarks shared by Jewelry-Auctioned.com.